Co-doping of hydroxyapatite with zinc and fl uoride improves mechanical and biological properties of hydroxyapatite

Hydroxyapatite(HA) co-doped with Zn2+ tand F- ions was synthesized by precipitation method for the first time in this study.FTIR spectroscopy revealed Zn2+ tand F ions incorporation into HA structure.Co-doping of Zn2+ tand F- ions decreased unit cell volume of HA and decreased grain sizes.Zn2+ tor 5 mol% F addition into HA significantly improved its density.Microhardness was increased with Zn2+ taddition and further increase was detected with F co-doping.Zn2+ tand F co-doped samples had higher fracture toughness than pure HA.Zn2+ tincorporation to the structure resulted in an increase in cell proliferation and ALP activity of cells,and further increase was observed with 1 mol%F addition.With superior mechanical properties and biological response 2Zn1 F is a good candidate for biomedical applications.     

结构非线性屈曲分析的有限元降阶方法

基于Koiter的初始后屈曲理论以及Newton法的增量迭代技术,提出了一种能够自动跟踪非线性平衡路径的降阶方法.降阶模型中摄动载荷以及主路径上变形位移的引入使摄动展开能够在平衡路径上的任意一点处进行;在每个摄动步中将求解降阶模型得到的非线性解作为结构响应的初始预测,然后采用有限元模型计算的残余力对解进行修正,最后以修正后的解作为下一个摄动步的已知展开点,并通过更新降阶模型来反映当前结构刚度的变化.算例分析表明,该方法不仅具有很高的非线性分析精度,而且需要计算的线性方程组(阶数与有限元全模型阶数相当)的数目远小于常规的非线性有限单元法.